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Tyroglyphid mites in stored products. Nature and amount of damage to wheat
Author(s) -
Solomon M. E.
Publication year - 1946
Publication title -
annals of applied biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.677
H-Index - 80
eISSN - 1744-7348
pISSN - 0003-4746
DOI - 10.1111/j.1744-7348.1946.tb06314.x
Subject(s) - wheat grain , biology , relative humidity , germ , humidity , zoology , toxicology , horticulture , agronomy , physics , microbiology and biotechnology , thermodynamics
The paper describes experiments and observations on the damage done by mites to stored grain, and methods of assessing the damage. It is confirmed that mites cannot penetrate grains if the grain‐coat is intact; but usually less than 10% of the grains are so intact. In laboratory experiments, mites consumed up to 3% by weight of the grain before dying out; they were able to destroy the germ completely, but consumed very little of the remainder; the maximum rate of consumption observed over a 5‐week period was 0‐29% of grain weight per week; when added to grain at 75% relative humidity in the proportion of 1% by weight, mites consumed 1% of the grain in 27 days at 21d̀ C, or in 37 days at 10‐15d̀ C. Although mites consumed the grain more rapidly at higher temperatures or humidities, they survived longer at lower temperatures or humidities, and finally did more damage. Mites consumed wheat germ flakes more rapidly than grain, and finally reduced its weight by 74‐85%. A system of symbols to represent degrees of damage to grain by mites, assessed visually, is presented, and approximate values for the equivalent weight losses are given. The relationship between the product, no. of mites per 100 ex. grain × time in weeks, and the degree of damage to grain, was calculated from experimental data; the damage done per unit of this density × time product was 2‐2‐5 times higher at 25 than at 5‐9d̀ C, and about 1‐4 times higher at 70 than at 90% relative humidity. The mean density × time value corresponding to 1% loss of grain weight was 526,000 at 250 C, and 1,765,000 at 5‐9d̀ C. Data from granary investigations show the degree of damage associated with various levels of population density and grain moisture. In infested storages, the amount of embryo material destroyed ranged from less than 1% of the total (bulk grain) to about 15% (grain in bags). Mites may cause a rise in the temperature or moisture‐content of grain, or an increase in the growth of microorganisms; but there is no evidence to suggest that serious damage from these causes is likely except that dense infestations can cause heating.